The invention relates to a device as well as a method for carrying out a blasting treatment of the inner wall of a channel with a stream of granular material, in particular, the inner wall of a metal pipe with a stream of metal balls (shot blasting).
The so-called ball or shot blasting is a known method for improving the strength of metallic surfaces; for example, during the maintenance of aircraft the front edges of the wings are acted upon with a stream of small metal balls. It is also already known to subject the walls of cavities in metallic objects to a blasting treatment, wherein the stream of balls is introduced into the cavity by means of a stiff lance having a longitudinal channel; if the wall of an elongated, straight cavity is intended to be treated with such a lance, a so-called interior blast nozzle is located at the forward end of the lance and the longitudinal channel of the lance opens into this nozzle which has a sloping surface which is inclined in relation to the axis of the lance and serves to deflect the stream of balls so that this exits from the blast nozzle transversely to the longitudinal axis of the lance.
This known device may be used for carrying out a blasting treatment of the inner wall of straight channels but not, however, when such a channel has one or more curvatures, as is the case for metal pipes which are used, for example, for stabilizers on motor vehicles as well as for the production of camshafts.
The object underlying the invention was therefore to provide a device of the type mentioned at the outset, with which the inner walls of channels which have one or more curvatures can be subjected to a blasting treatment, in particular, the inner walls of metal pipes having at least one curvature.